at what point do u have to upgrade expecially if u tow heavy before any damage happens ?

With an empty truck, around 100hp is the save level. Towing you are going to want to keep it at 40-60hp extra.

get something like the juice that will monitor EGTs and tranny, you will be glad. no harm below 100HP, just dont flog it all the time :D

The Juice will only monitor egt with the addition of the Attitude. Really a great piece for the LB7. I have slipped my tranny on the 100 HP setting, but I was really flogging it.

at what point do u have to upgrade expecially if u tow heavy before any damage happens ?
Towing heavy at stock power levels can and will hurt the transmission. With that said it's all in how you treat it. If you beat on it you will hurt it, if you drive easy and pull upto speed without going WOT all the time a LB7 equipped truck will hold about 80 RWHP and a LLY will hold about 60 RWHP. Power levels above these will kill the transmission.